Effect of Sb Addition on Hot Tearing Susceptibility and Mechanical Properties of Mg–7Al–1Ca–xSb (x = 0, 0.5, 1, 1.5, and 2 wt.%) Alloys

The effect of Sb addition on the hot tearing susceptibility (HTS) of Mg–7Al–1Ca–xSb (x = 0, 0.5, 1, 1.5, and 2 wt.%) alloys was studied using a “T-shaped” hot tearing measuring system and differential thermal analysis experiments. The mechanical properties of the alloys were investigated using tensile tests. The crystal phases of the alloys were analyzed by X-ray diffraction and energy-dispersive X-ray spectroscopy. The microstructure and the morphology of the crack zone and the tensile fracture were characterized by optical microscopy and scanning electron microscopy. The results showed that the HTS of the alloys first decreased with Sb addition up to 1.5 wt.% and then displayed an increase with Sb addition up to 2 wt.%. The addition of Sb refined the structure, made the distribution of the second phases more homogeneous, and improved the skeleton strength, thereby reducing the HTS of the alloys. However, when the Sb addition reached 2 wt.%, the low-melting-point eutectic phases that could participate in feeding reduced, resulting in an increase in the HTS of the alloy. Additionally, the mechanical properties of the alloys were improved after adding Sb. Among them, Mg–7Al–1Ca–1Sb alloy exhibited the optimal ultimate tensile strength, yield strength, and elongation with the values of 203 MPa, 133 MPa, and 8%, respectively.